Intro to Percolation Theory: Two Takes On The Classic But Rare Harmonic Percolator

Published October 29, 2014

Intro to Percolation Theory:

Two Takes On the Classic But Rare

Interfax Harmonic Percolator

by Christopher McTernan

The Interfax Harmonic Percolator is amongst the most unique-sounding fuzzes ever produced. Designed by Milwaukee electronics repairman Ed Geise in the 1970s, it distinguished itself by utilizing both germanium and silicon transistors to cancel out odd-ordered harmonics and amplify even-ordered harmonics. Even-ordered harmonics are perceived as being more “pleasant-sounding” to the human ear. The Percolator gained popularity after guitarist/recording engineer Steve Albini (Big Black, Rapeman, Shellac) used it to further his aggressive guitar tone. To many budding young math-rockers and post-punkers the Percolator became known as the “Albini pedal.” Ironically, it was only a small part of an elaborate and thoughtfully designed guitar set-up for Albini and by itself doesn’t replicate his distinctive guitar sound. This hasn’t stopped Shellac fans from seeking out Albini’s secret ingredient to his buffet of noise. Unfortunately for them, the original Interfax version is rarer than Bigfoot. Geise only constructed a small number of Percolators, meaning that few fuzz-lovers have had the opportunity to see the real McCoy up close and personal. He was also secretive regarding the parts that he used and was rumored to have hidden the key components via strategically-placed epoxy inside the pedals. But where there’s a will, there’s a way, and enterprising young pedal builders began creating their own clones of Geise’s circuit.

Chuck Collins was a builder and admirer of the original Ed Geise circuit. Under his brand name Theremaniacs Collins created what has become the most well-known Percolator clone. He even reportedly managed to trademark the name Harmonic Percolator for his creations. Collins claims to have reproduced what he says is the best circuit/version of Geise’s pedal (Collins states that Geise had made 4 variations of the Percolator), the same circuit as the version favored by Mr. Albini.

Pictured: Catalinbread Karma Suture

A number of other builders followed suit over the years. The latest one to hit the market is the Catalinbread Karma Suture. The Karma Suture, unlike the Theremaniacs/Chuck Collins Percolator, is not a straight-ahead clone of the Interfax version. It takes the basic idea of using both PNP germanium and NPN silicon transistors and expands upon that by adding a few welcome tweaks to the concept. One of the issues many players experience with the Collins Perc is a lack of output on the lower gain settings, causing a perceived drop in volume when engaged. Pulling the two levers (essentially gain and volume, or input and output) ¾ up or higher would alleviate this volume drop but also would add more gain, making it hard to get a lightly distorted tone without losing volume. It also loses low end as the gain is increased. The Suture alleviates this issue by adding both a “Diode” and a “Density” control. The Density is essentially a tone knob although it doesn’t get as “wooly” sounding at the 7-10 o’clock settings as other overdrives/fuzzes/distortions do. It retains a nice clarity in all “density” settings. So maybe “thickness” would be more appropriate than “tone”. “Diode” seems to color the tone pleasingly. Catalinbread describes it as being a control for how much signal is sent through the diodes. The Karma Suture is also sturdily built; a little hot pink box that can take a beating. The open slot sliding controls of the Perc leave it open to the mercy of the stage or practice space, leading inevitably to dust/dirt/beer/etc. finding its way into the slots of the sliders. Still, the Perc’s more understated and clinical look befits a pedal that is so beloved by nerdlinger post-punk fans (such as yours truly). The Suture power adapter input is a welcome addition as the Perc can drain batteries in short time.

Pictured: inside the Collins Percolator

As a circuit that is notorious for its explosively aggressive sound, both pedals live up to their reputation. However the Collins Perc is more aggressive sounding when pushed to the max and it interacts with other gain boxes in a very unique way. Swapping in and out various boosts, fuzzes, and distortions in front or behind it can lead to pleasant surprises. The Suture also plays nice with other drives but lacks that element of mystery and happy accidents that you get with the Collins Perc. Overall the Suture is a welcome addition to the Percolator family, giving more control over the tone in a sturdy small format package.

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